<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script type="text/javascript">
    var a=parseInt(prompt("请输入一个数"));
    var b=parseInt(prompt("请输入一个数"));
    var c=a+b;
    if (c>=100){
        alert(c-100)
    }else {
        alert(c)
    }
</script>
</body>
</html>